O f stew jeesey



Patented Sept. 26, 1922.

UNITED .S'IATES 1,430,11 FATENT' OFEFMIE.

RALPH EL RINDFUSZOF NORTHAMPTON, AND VANDERVEER VOORHEES, OF HOLYOKE,

MASSACHUSETTS, ASSIGN ORS T0 AMERICAN WRITING PAPER COMPANY, OF HOL- YOKE, MASSACHUSETTS, A CORPORATION OF NEW JERSEY.

PROCESS FOR RECOVEEING TILAX FIBER.

1N0 Drawing.

To all whom it may concern i the United States, residingat Northampton, in the county 'of Hampshire, and Holyoke, in the county ofHampden, respectively, in the State of Massachusetts,.have invented certain new and useful Improvements in Processes for Recovering Flax Fiber, of

which the following is a specification.

'This invention relates to a process for recovering clean fiber from flax straw or flax tow. y

The straw of the fiber flax plant is at present subjected to an elaborate retting process for the isolation and recovery of fiber for use in the textile industry; and in the combing and carding operations necessary in the production of the clean fiber, a by-product is combed out, consisting of a tangled mass of fiber and woody shlves which is known as flax tow. Like-- wise in the threshing of seed flax, a slightly different plant than fiber flax, for the recovery of seed, the straw by-product has been subjected to mechanical and chemical processes in order to remove in large part the woody shives from the straw and again produce a flax tow.

Flax tow is at present used --in the upholstery arts and for similar purposes and if sufficiently refined bythe removal of the objectionable shives is also used in the manufacture of fiber board, counter board,

Straw in the Paper and Fiber-Board In- In none of the prior processes or experiments has it been possible to remove or reduce all the shives from the fiber of the flax tow without impairing the strength Be it known that we, RALPH E. RIND FUSZ and VANDERVEER VoonHEns, citizens of An account of Applicationfiled November 15, 1919. Serial No. 338,299.

and usefulness of the fiber itself either for paper making or other purposes. The prior workers in the art were compelled to be satisfied with a moderate degree of success which enabled them to sufiiciently refine the fiber for heavy grades of paper and fiberboard although a clean fiber entirely free from unreduced shives would have been highly prized as stock for high grade writing papers, parchment and pure linen papers.

The resent invention therefore is for a method for cleaning substantially all of the shives or unreduced woody material from the fiber of the straw and for producing a fiber suitable for the manufacture of the finest grades of writing paper as well as for textiles. An important chemical principle upon which the present invention is based is that cold nitric acid, i. e. at ordinary room temperature, either alone or in combination with certain other acids, will not deleteriously attack the fiber of flax straw or tow but will attack and reduce the woody portion or shives, which, as is well known, comprise cellulose fibers associated with encrusting or adsorbed lignin. In the application of this principle although nitric acid alone is effective, it has been found that sulphuric or hydro-chloric acid added to nitric in a cold mixture will improve the action slightly and also that various other acid compounds of nitrogen may be employed for the reduction of the shives such, for instance, as nitrous acid, or a nitrite salt together with a suitable reagent for the release of the nitrous acid. After the shives of the flax tow or straw have been reduced by the action of the nitric or nitrous acid and the cellulose fibers thereby set free,

the gelatinous substance derived from the lignin or other non-cellulosic components is easily washed and separated from the fiber by any of the well known alkali cooking and washing processes.

As a preliminary treatment, before subjecting the tow or straw to the nitric acid or its equivalent, it is preferred to cook the tow in one of the usual alkali compounds such as milk of lime, which will reduce a large part but not all of the shives. After the alkali treatment the fiber should be washed thoroughly in water to remove alkali and products derived from the Woody material: and then subjected: to the nitric acid treatment. At the end of the acid treatment the fiber should be again washed to remove the acid and finally given another alkali cooking treatment this time preferably with a comparatively dilute solutionof caustic soda to complete the removal of non-cellulosic shive material. Thereafter the fiber is washed clean in water and is ready for the bleaching agents and other operations in the manufacture of paper or textiles.

A more particular description will now be given of the steps at present preferred for carrying out this process although it will be understood that considerable variation in the mechanical devices, degree of temperature, duration of time and proportions of materials may be made and still obtain a satisfactory working of the process.

The flax fiber in the form of tow or straw is first cooked with 20% of its weight of milk of lime Ca(OH) which may be effected in a closed cylinder into which steam is introduced for heating the same.. The steam is maintained at a pressure of about 50 lbs. for about three hours and the cylinder should be rotated slowly for the purpose of agitation.

At the end of this period the fiber is removed, drained of its alkali liquor and washed in water in a suitable washing ma. chine-or beater and then pressed dry.

The pressed fiber is then placed in an acid tank containing about 40% of the fiber weight, of a cold acid mixture made up of equal pro ortions by weight, of sulphuric acid, H 8 4 and nitric acid HNO; and is agitated in this cold acid mixture for about five hours. By a cold acid mixture is meant that the acids are kept at ordinary room temperatures approximately 70 F. An acid mixture containing equal proportions by weight of nitric acid and hydrochloric acid HCl may also be employed in this step in place of a mixture of nitric and sulphuric acids.

Furthermore, this acid treatment ma if desired, be effected with nitrous acid H in which case the pressed washed fiber is placed in the acid tank with a solution containing 10% of the fiber wei ht of sulphuric acid H,SO,, and during t e agitation a concentrated solution of sodium nitrate NaNO containing 10% of the fiber weight of NaNO is admitted at intervals to the bottom of the acid tank containing the acid and fiber. The reaction liberates nitrous acid to act on the shives of the fiber. The fiber is preferably agitated in this solution for about six hours and in this nitrous acid treatment it is not so essentiah to prevent the acid mixture becoming heated slightly above ordinary room temperatures.

After the acid treatment the fiber is rev moved, drained and again wadaed in water in a suitable washing machine to firesthe fiber from acid.

Thereupon thefiber is again cooked in an alkali preferabl in a closed cylinder with about 40- to 50' bs.ofi steam pressure: suitable alkali for this step being caustic soda N aOH in pro ortion of about 5% of the fiber weight. he fiber is thoroughly agitated during this-cooking process which is continued for about two hours.

At the end of the final. alkali cook, the fiber is removed and a sin thoroughly washed in water after whidh it is ready for being bleached. in the usual manner. The fiber will now be entirely free of unreduced shives and it will be found practically unim aired in strength so that it is suitable bog; for paper and textile manufacturing, processes.

The pulp prepared in the manner described above is quite free from unreduced shives and is suitable for the manufacture of high-grade white or tinted papers, with satisfactory yields from the original tow or straw. The treatment described is effective for the breaking down of the woody or shive material, and the isolation therefrom of the shive fibers; which latter remain to a large extent in the paper and. ma be readily identified therein, along wit the best fiber of the flax, by their characteristic forms and behavior toward fiber stains.

What we claim is 1. Process of preparing high-grade paper pulp from flax tow, comprising subjecting the tow to an alkaline cook under an eratmospheric pressure to soften the ive material; removing the alkali and treating, at substantially normal temperature with an acid solution comprising an oxy-acid' of nitrogen; and completing. the removal of: ligneous' shive material by a further aIka. line treatment.

2. Process of preparing, high-grade paper pulp from flax tow, comprising subjecting; the tow to an. alkaline cook under superatmospheric pressure to soften the shive' material; removing the alkali and treati at substantially normal temperature wit an acid comprising sulfuric acid and an oxy-acid" of nitrogen; and completing the removal of ligneous shive material. by a further alkaline treatment.

RALPH E. RINDFUSZ'. VANDERVEER VOORHEES. 

